As used herein, the term "modification ratio" ("MR") describes the ratio of the radius of the circle circumscribing the lobes of a lobal fiber to the radius of the circle inscribed by the core of that fiber. The term "fiber" encompasses both staple fibers and continuous filaments. "Yarn" means a continuous strand of fiber in a form suitable for knitting, weaving, or otherwise intertwining to form a fabric.
Synthetic fibers used to make carpet yarn and ultimately carpet must possess certain characteristics in order for the carpet made from these fibers to be durable and satisfactory floor covering. Due to high volume foot traffic, carpets tend to become dull, dirty and reveal paths where people habitually tread, e.g., the center of a hallway. As a consequence, carpets should resist soiling for long periods and hide any soil which does accumulate. As a further attribute, a carpet should be resistant to staining by materials commonly found in households and commercial environments. One notorious source of staining is the acid dyes found in beverages like fruit juice and colored children's drinks. Various efforts have been directed to producing carpet fibers which possess as many of these attributes as possible.
Hollow trilobal fibers are known to generally provide soil hiding characteristics when used to make carpet. For example, U.S. Pat. No. 5,208,107 which issued May 4, 1993 describes a hollow trilobal fiber.
Providing nylon polymers with reduced amine end group levels is known. For example, U.S. Pat. No. 4,097,546 to Lofquist describes the use of monocarboxylic acid or dicarboxylic acid as a molecular weight regulator which also decreases the concentration of amine ends, preferably to 15 to 25 meq/gm. Reducing amine end group levels contributes to acid dye resistance by blocking the amine receptors for acid dyes.
Application of fluorochemicals to yarn is known to resist soil and repel oil. For example, U.S. Pat. No. 4,192,754 to Marshal et al. describes a spin finish containing a fluorochemical compound.
Stainblockers for imparting acid stain resistance to polyamide carpeting yarns are known as well. While present stainblocker technology encompasses several chemical classes, of most concern here are certain aromatic-formaldehyde condensation products, some of which are also known as novolacs, and other sulfonated materials. U.S. Pat. No. 5,061,763 to Moss III et al. describes a stainblocker composition which is prepared by polymerizing an acrylic monomer in the presence of sulfonated aromatic-formaldehyde condensation products. Patents describing the use of novolacs as stainblockers for carpets are U.S. Pat. No. 4,822,373 to Olson et al., which describes a polyamide treated substrate having applied thereto a mixture of partially sulfonated novolac resin and a polymethacrylic acid or copolymer thereof. U.S. Pat. No. 4,780,099 to Gresschler et al. describes polyamide fibers which are made stain resistant by treating them with a sulfonated naphthyl or sulfonated phenol formaldehyde condensation product at a pH of between 1.5 and 2.5.
Various ingredients including sulfonated phenolic resins, sulfonated aromatic compounds, compounds of sulfonated phenolics and aldehydes, modified wax emulsions, fluorochemicals, acrylics and organic acids of low molecular weight have been variously combined to provide stain resistance upon application to polyamide carpet. For example, U.S. Pat. No. 5,073,442 to Knowlton et al. describes such a composition.
Yet, most efforts to combine various known agents onto the fiber itself have been unsuccessful to some degree. Most efforts to combine various known agents to carpet yarn for soil repellency and stain resistance have been only partially successful and then only at relatively slow speeds (less than 100 mpm). Some of the difficulties encountered include incompatibility of fluorochemical finish and stainblocker, tackiness of the stainblocker and migration of stainblocker to the fiber center. Surprisingly, the present invention allows a particularly effective treatment to carpet fibers through control of application conditions at high speeds. The fiber produced by this process has excellent properties that were previously unachievable in a fiber. These properties include improved soiling and staining resistance, soil resistance, superior cover, superior appearance retention, low flammability, a firm hand and ease of processing.